While using this tool I'm bearing down on it as I guide it over the sheet.  Making deep impressions into the metal is the purpose. This also to helps to align the tool since I haven't attempted to set guide lines or channels first for the bit to follow.  The idea is to create random unpredictable areas stamped into the sheet. If one is using this type of tool for prolonged periods at a time then I'd recommend wearing a cushioned palm glove that's made for this purpose.  It may help to prevent some problems with carpal tunnel syndrome.  For intermittent work then I wouldn't worry very much about it.